1. Field of Invention
The present invention relates to dimmable- electronic ballasts for fluorescent lamps, particularly of a kind wherein cathode heating power is removed during periods of full light output and restored during periods of reduced light output.
2. Elements of Prior Art
Fluorescent lamp ballasts designed to permit wide-range control of light output provide cathode heating at all times; otherwise, during periods of reduced light output, lamp life would be seriously foreshortened.
Yet, as is well known, efficiency may be significantly improved by removing cathode heating power, especially during periods of full light output.
As is also well known, during periods of full light output, cathode heating power may be removed without suffering serious foreshortening of lamp life.